Head flow testing.
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Fast Eddie
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comnoz said:Fast Eddies RH10 head before and after a street port job with 3mm oversized intake valves.
I thought I'd post this update in Jims thread to make it easier for folk searching this topic.
More info on this topic fine build can be found here:
engine-build-prep-t18461-165.html?hilit=Cylinder%20head%20testing%20Dyno
Jim's graph is based on the following 'before and after' specs:
'Before' spec of bike was: JS1 cam/ follower/ spring kit, JS rods and pistons at 10.5:1 CR, nice squish (forget exact measurment), 35mm FCRs, cNw manaiflod, Tri spark, cNw coils and leads. Standard RH10 head and valves.
'After' spec is: as above plus, followers ground to 7/8th radius instead of 1 1/8, 3mm OS re-angled inlet valves, 1.5mm OS exhaust valves, Comnoz port job, Comnoz valve springs.
Actual peak figure was 64.6bhp @ 6300 rpm, with a very flat power graph from 6000 to 7000. This was a 9bhp (yes NINE BRAKE HORSE POWER, on the same dyno) improvement!
There was significantly more power everywhere from 3000 upwards.
I was very surprised by this to be frank, the improvement way exceeded my expectations.
The summary is that the RH10 head, reworked by Comnoz, gives an outstanding performance improvement. The BHP per $ ratio being far more favourable than most (any?) other mods that I can think of!
Sending your RH10 head to Comnoz should be a compulsory requirement of ownership...!
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I use JBweld on a roughened floor in BSA A65 ports. Never had a problem. Only inlets naturally.
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That's fantastic to see. I've been trying to figure out why a ported head on a stock A65 650 makes so much difference both in response and top end. The response is really nice and instant. I have vacuum cleaners and measurements based on a std BSA port being 109cfm and basing calculations on it. The numbers are just what it gives and probably optimistic, but the relationship is indicated. The red and the green line are through a 34mm PWK. I have stuff to make something to measure port velocity which I can compare when I get time.
The head with the green line works far better than expected on a std engine which I plan dyno testing because of curiosity. It also works on a long stroke 745, not dynoed but 8 wins from 10 starts a 2nd and a dnf, and Queensland P3 sidecar champions.
Please ignore the numbers as it's embarrassing if they are over optimistic. My bench is just a measure that works but of dubious accuracy.
The green line uses a 42mm valve the redline a 44.5mm valve and though it flows more through the 34mm carb I have no idea how it might work. Air has to go faster through the carb but after that in the bigger port I don't know. It's for an 80X74 90 degree, but it needs grunt as well as rpm.
If you look where the gasket is that's the shape as it enters the head. With the big valve the entry is the same but it gets bigger for the valve.
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I've been using a manometer with plastic hose in the port to get an idea of velocity. Hope I am doing it right. Vizard has a chart reading up to 38"w which equals around 400fps. That approximates speed if the bench is testing at 28"w... in theory. Depending where I put the hose end I can get 34" 380fps just in the manifold, 40" 420fps in the port and down near the guide 52" probably 450fps? But that's beyond his graph. It varies depending where it is, it seems fast on the short turn, not that I can see it so well and the hose in there probably affects it.
The port flows well cfm wise, and reducing the bench test pressure to half (14") still has 30" or 360fps in the port. What I don't know is what the engine will pull and what speed may be like on a running engine. This is on a BSA A65 head with 34mm port and 44.5 valve. I also have the same thing with 42mm valve that works well on an engine which I should compare and then a stock port and maybe try mapping as you have above. This is that 34mm manifold transitioning to oval entering the head. It's about 70% more flow than stock 30mm at stock full lift.
This is using a port shape based on the XR750 oval port. As Jim at JSmotorsport talks about often. These threads are extremely interesting and your work. I hope me commenting isn't too annoying. This is an old head with lots of patching in it. Except for the floor it wouldn't need patching but not all cast in seats line up to take 44.5mm valves. Because I was patching this I moved the port down a little and lined it up better.
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Mark writes: " I've been trying to figure out why a ported head on a stock A65 650 makes so much difference both in response and top end."
I have read that the A65 head responds well to work on the ports because they were never built in the factory to the original design specifications. This might be part of the answer.
I have read that the A65 head responds well to work on the ports because they were never built in the factory to the original design specifications. This might be part of the answer.
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I think what that refers to is related to the Spitfire head of 1968 #68-915 they had special ports deeper and wider in the bowl. There is a detailed engineer's drawing. It meant a Spitfire with 9-1 comp and 32 Concentrics could make 56.5hp. The factory did not extend that improvement to the standard models, only those Spitfires. The different head didn't even make it into the parts book, the 68-701 was still listed. In 1970 Umberslade engineers built an engine with head ported to 'the drawing', I expect it was that one. Looking at a '71 head in the bowl area, it isn't that noticeable without measuring, but it is as that Spitfire drawing. It's not great but measures around 120 or 122cfm an improvement on the 68-701's 109cfm. The '71 head used the 30mm carbs.
What I was talking about was a stock engine with 34mm carbs and 42mm valves that's a bit of a shock when you open the throttle at any rpm and goes crazy on full throttle. A standard clutch is no where good enough. It's what Fast Eddie describes with his Norton with its ported head, it doesn't just improve top end but also midrange. It's a very nice thing, you don't go flat out all the time, but using a bit of throttle in the midrange is nice when it feels so strong. His 64.6hp at the wheel equates to around 73.3hp at the crank which is very decent. Why I'm wanting to measure what this 650 has.
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Speaking of BSA's, Fred Barlow Spares (FBS) ported the head on my 750 powered P11. I read somewhere that he was a BSA guru. I don't know what any of the charts would look like with my motor, but it works everywhere with that FBS head on it, and works a lot better than an early stock Commando 750 head. I had a stock Commando head on it when the port work was being done. Felt like I was riding in sand pulling the Queen Mary with the stock head by comparison. It is not hogged out. It is just done right for a hot street Norton. Hot being relative to stock late 60's 750 twins.
I only have one trophy for my P11, and I got it at a car show.
I only have one trophy for my P11, and I got it at a car show.
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